Not Applicable.
Not Applicable
1. Field of Invention
This invention relates to alarm systems, and more particularly to a perimeter monitoring system which uses infrared links to create a boundary through which intrusion is detected.
Still more particularly, the infrared links of the perimeter monitoring system may optionally be synchronized so that the infrared transmitter for one link will not falsely be received by the receiver of another link and, optionally, breach information can be transmitted to a base location.
2. Description of Prior Art
Personal and property security has long been a concern and continues to be as evidenced by increased utilization of automobile and house alarms systems. The most prevalent type of alarm is that of intrusion detection, where incursion into some defined area is sensed and indicated with either an overt broadcast alarm, or a covert alert, e.g., an automatic telephone call to the police. A example of this is a simple automobile alarm which is triggered by the opening of doors (the existing door button that activates the internal dome light is often used). In this case access to the protected area, the internal space of the car, is generally made at specific locations, i.e., the car doors, and only these are sensed. (Of course, more sophisticated car alarms may include motion sensors so that window entry is also detected). Another example of existing intrusion detection systems are the many house alarm systems available. Here the detection methods can be separated into two general categories: 1) internal presence detection, and 2) perimeter violation. Examples of the former are proximity motion and heat sensors. In the latter case, as in the car alarm, advantage is taken of the fact that entry is generally made via specific locations, e.g., windows and doors, and sensors are thus placed at those points. Internal presence detection via proximity detectors can be very effective but have two drawbacks: they can be tripped unwontedly by pets, and by their very nature only alarm after premises entry has already been made. A perimeter security system consisting of a series of door and window sensors, on the other hand, although often times more difficult to install, can provide secure protection along with free internal movement. Of course, many home protection systems include both categories for optimum security.
Another example of perimeter violation protection, and one that encompasses a larger area, is estate property that is bordered by an entry-resistant wall. Here, again like the car alarm and the house perimeter sensors, entry is limited to specific locations, in this case the driveway, and an intrusion sensor is placed only there. Unlike the perimeter sensors used in a house system that need only detect, for example, that a window or door contact has been broken, however, the sensor method used here must detect an intrusion through a span of open area, e.g., the driveway opening in the wall. A point-to-point infrared transmitter/receiver pair can serve this purpose and U.S. Pat. No. 3,370,285 describes one such system. Here, an infrared beam is established between a transmitter and receiver placed at either end of the span to be protected. Cessation of the beam reception by the receiver caused by, for example, an intruder constitutes an area violation.
The Tandy Corp., via their Radio Shack line of stores, offers a similar system, however here the transmitter and receiver are contained in a single unit which could be placed at one side of the protected span, while an infrared reflector is placed at the other end, so that the beam travels twice across the span before being detected by the receiver. The operational effect is the same as U.S. Pat. No. 3,370,285, however, the Tandy system has the advantage in that all of the electronics, and thus the powering requirements, are contained in a single unit.
Another point-to-point light beam alarm application is described in U.S. Pat. No. 4,998,093. Here a light beam emitter and separate photoelectric detector are used to protect road workers by detecting when errant vehicles have crossed into the road work area. When the light beam is broken circuitry associated with the photoelectric detector transmits radio frequency warnings to radio receivers worn by each worker in order to communicate a potential danger alert.
A more difficult alarm protection situation occurs when an open area needs to be secured. In the estate example above, for example, if no effective deterrent wall exists, then the single point-to-point detection scheme is inadequate since instead of a short open span to protect, now an entire perimeter must be secured. Other examples of open areas that would be desirable to protect would be for campers in remote areas, or small children in play areas (here the need would be to contain the children within the area, rather than alarm against intrusion from without). A common approach is to use a series of proximity sensors to create a detectable perimeter. U.S. Pat. No. 6,118,375, for example, describes a portable proximity sensing apparatus that could be used as a component in such a system. Here multiple of these devices are placed so as to create a perimeter around the protected area whereby each can sense motion within a circle in its proximity, and the devices are placed so that the series of resulting protected circles overlap and create a complete secure perimeter. Motion above some threshold causes the detecting device to generate a warning by audible alarm, flashing lights, or a combination of the two. The great disadvantages of this type of system are three-fold: firstly, in open areas outdoors proximity sensors are easily susceptible to false triggering due to wild or tame animals, or due to wind causing movement of buses and tree branches; secondly, the very nature of proximity sensing reduces the perimeter usable area since the zone of detection is defined by the inner limit of each detectors range (and additionally disadvantageous since it is difficult for the users to know precisely where this boundary is); and thirdly, the alarm methodxe2x80x94audible or visual warningsxe2x80x94would serve to warn an intruder as effectively as the user.
More precisely defined perimeter protection methods have been proposed using wires. U.S. Pat. No. 4,091,367 describes the use of parallel-placed leaky coaxial cables to detect movement of human-sized objects past them via perturbations of RF signals continuously propagated around the cables. Alarming is provided at a base location where RF transmission and reception occur, and can take various forms, including methods that would be undetected by an intruder. Although this scheme solves the proximity detection problems of an ill-defined perimeter and warnings made to the intruder as well as to the user, since it is based on threshold detection of RF energies it remains to some degree susceptible to either false triggering on one hand, or undetected intrusions at the other. Additionally, this scheme could be cumbersome to deploy in remote, temporary situations, such as a camp area.
Another method of precisely defining a secure perimeter involves using a series of point-to-point light beam span protections. U.S. Pat. No. 4,978,942 describes one such system using infrared transmitters and receivers that are enclosed in containers camouflaged to appear as ordinary industrial storage drums. The patent disclosure describes that these units could be placed in series, presumably such that the transmitter of each is associated with the receiver of the next device in the perimeter. Warnings of intrusion are sent via radio frequencies to some base location for alarming. Although this scheme also solves both the problems of the ill-defined perimeter and warnings made to the intruder, it includes the undesirable complexity of radio links which themselves can be prone to unreliability due to natural and manmade interference.
Finally, U.S. Pat. No. 4,998,093 mentioned earlier describes the use of a reflector to create angles in the line of protection. One could imagine a series of reflectors placed in a circle such that the transmitted light beam is carried around a perimeter back to a receiver placed next to the transmitter, however, due to the unavoidable dispersion of light energy the light beam would be either spread or attenuated greatly with each reflector so that such a scheme would be impractical with more than one or two reflectors. A laser source could solve this problem but adds its own level of complexity, and in any case, acquiring precise alignment of multiple mirrors is a relatively difficult task not suited to temporary applications.
What is needed is a method to protect an area which defines a precise breach boundary and which is simple, reliable and inexpensive, and which is not detectable by an intruder.
Therefore, in accordance with the present invention a method for detecting intrusion into, or exit from, an established continuous perimeter or boundary uses infrared energy to create linking beams between multiple transceiver node devices placed at intervals around the perimeter or along the boundary. For perimeter applications each transceiver node device along the perimeter receives from a neighbor transceiver node device in one direction and transmits to another transceiver node device in the other direction forming a circle of infrared-linked transceiver node devices. One of the transceiver node devices serves as a base unit device to provide indication of perimeter violation, e.g., via an audible alarm or visible light indication. If any infrared beam link is obstructed, as would occur, for example, when an intruder enters the perimeter area, the receiving transceiver node device upon detecting a loss of infrared energy acts to suppress its infrared transmission. Since each transceiver node device operates in the same way, each subsequent transceiver node device around the perimeter will, in turn, detect a loss of its infrared input and consequently suppress its transmission until finally the base unit device detects that its infrared input has been lost in which case it indicates an alarm. In this way a breach anywhere around the perimeter is communicated to the base unit device.
Additionally, the infrared energy comprising the inter-device links can include a signal in order to provide perimeter coordination and to communicate specific information to the base unit device. For example, the transceiver node devices forming a secure perimeter, might include signal patterns unique to each transceiver node device in the perimeter. Each transceiver node device""s unique signal pattern is derived from its self-deduced position in the perimeter. By using signal patterns that are unique to each transceiver node device, a receiving transceiver node device is able to distinguish the previous transceiver node device""s transmission from others in the perimeter, thus ensuring that perimeter intrusions are detected since otherwise a link break might go undetected if the receiving transceiver node device is still receiving the infra-red transmission from another unit. Also, rather than simply suppressing its infrared transmission when a transceiver node device detects a perimeter breach via a loss of its infrared input, it could alternatively transmit a unique alarm indication that includes its identity. In this alternative embodiment each subsequent transceiver node device in the perimeter relays this signal so that ultimately the base unit device not only is informed that a perimeter breach has occurred, but is also informed at which infrared link the breach occurred, i.e., the link immediately previous to the transceiver node device associated with the identity included in the alarm signal ultimately reaching the base unit device.
Alternatively, instead of linked nodes arranged in a closed circle, one node provides only the base unit transmission functions and serves as a source of infra-red transmissions. Linked nodes are then strung together as in the perimeter application ending with the base node which in this arrangement provides infra-red reception and alarm functions, but does not provide infra-red transmissions. In this way a non-enclosed boundary can be established and intrusions across the boundary can be detected.
Yet another arrangement uses more than one infra-red transmission source node, each feeding branches of a tree-structure that ends in a single alarm base unit. Nodes located at the tree""s branch junctions contain multiple infra-red receivers and any received alarm indication, be it loss of infra-red reception or breach information, is passed on to the next node downstream towards the base unit. In this way complex boundary arrangements can be protected as might be used in a building structure with multiple rooms and hallways.
As an aid to initial setup, the linking node devices are placed into a special calibration mode in which the user is provided visual indication as to the alignment of the transmitted infrared beam from one node with the infrared receiver of another node.
Accordingly, some objects and advantages of the present invention are:
a) to provide a method for securing an area such that entrance into, or exit from the area through a defined perimeter is detected,
b) to provide a secure perimeter such that the detection method operates on the precise boundaries of the defined perimeter,
c) to provide a secure perimeter using devices that are simple to use and low in cost to manufacture,
d) to provide a secure perimeter that does not rely on radio frequency transmissions which could be detected by a potential intruder who would thus be warned to attempt alarm circumvention,
e) to provide a secure perimeter that uses devices that receive infrared energy from one direction and transmit infrared energy in a different direction so that such devices can be linked transmit-to-receive in a continuous loop, thus creating the perimeter to be secured,
f) to provide a secure perimeter using the aforementioned linked infrared transceiver node devices that upon detecting that their receive infrared link has been lost, indicating a possible perimeter breach, change their infrared transmission such that subsequent devices around the perimeter are informed of the breach,
g) to provide a secure perimeter using the aforementioned linked infrared transceiver node devices that includes a base unit device for providing alarm indication,
h) to provide a secure perimeter using the aforementioned linked infrared transceiver node devices whereby each device upon detecting that their received infrared energy has been lost suppresses their infrared transmission so that a breach causes all subsequent devices to suppress their transmissions until finally the base unit device is informed of a perimeter breach by the fact that its received infrared energy is lost,
i) to provide a secure perimeter using the aforementioned linked infrared transceiver node devices whereby alternately a device upon detecting that its received infrared energy has been lost changes its infrared transmission such that it now includes a perimeter breach indication, and subsequent devices around the perimeter change their infrared transmission accordingly so that a perimeter breach indication is again carried around to the base unit device,
j) to provide a secure perimeter using the aforementioned linked infrared transceiver node devices whereby alternately a device upon detecting a perimeter breach due to loss of received infrared energy includes in its infrared transmission both a breach indication as well as an indication of its position in the perimeter, and that this position indication is transmitted around the perimeter to the base unit device,
k) to provide a secure perimeter using the aforementioned linked infrared transceiver node devices whereby each device comprising the secure perimeter automatically detects its position in the perimeter,
l) to provide a secure perimeter using the aforementioned linked infrared transceiver node devices whereby each device distinguishes between the unique transmission of the previous device in the perimeter and those of other devices,
m) to provide a secure perimeter using the aforementioned linked infrared transceiver node devices whereby each device includes a means to aid in adjusting the transmit/receive alignment of two adjacent devices in order to optimally establish an infrared link.
n) to use a source node that provides initiation of infra-red transmission separate from the alarm-function base node so that breaches of non-enclosed boundaries can be detected,
o) to use a multiple of such source nodes so that multiple boundary branches can be protected, converging on an alarm-function base node.